Preservation of active atrial transport; an important clinical consideration in cardiac pacing.

Loss or reversal of the normal sequence of atrioventricular contraction, such as occurs during ventricular pacing, can significantly reduce cardiac output. Opinions vary regarding the size of the pacemaker population that might benefit from preservation of active atrial transport during cardiac pacing. An assessment of 260 consecutive patients who underwent implantation of a permanent transvenous pacemakers by the authors between 1970 and 1979 revealed 19 patients who had clinical symptoms or hypotension when active atrial transport was lost. Thirteen patients were symptomatic with syncope, dizziness, shock, heart failure or cough; six were asymptomatic but had systolic blood pressures lowered to the 80-100 mm Hg range. In all instances but one, attempts were made to restore atrial transport by one or more of the following methods: replacement of the pulse generator with a slower, single rate generator to minimize pacer competition with the normal sinus mechanism; slowing the rate of a programmable unit; implantation of an atrial pacing system; implantation of an atrioventricular sequential pacemaker system. Restoration of the normal sequence of chamber activation by any of these methods eliminated the symptoms and stabilized arterial blood pressure. We conclude that preservation of active atrial transport was clinically important in 7.3 percent of our heterogeneous permanent pacemaker population.